the current major java versions related to wM versions are:
Java 1.5 for wM 7.1.x (Update to Java 1.6 possible, but requires some adjustements)
Java 1.6 for wM 8.2.x (Update to Java 1.7 possible, but might require some adjustements)
Java 1.7 for wM 9.x
Broker does not really require Java as it is written in C.
But it has some APIs (Java, JMS) which can be (resp. are) used to connect to broker from java applications, i.e. MWS, IS, PartnerSystems.
Older APIs should work in newer Java versions but not vice versa.
But the question I ahve raised for the version 6.5 where I can see IS uses Java version 1.5 and Broker Java version uses 1.4. As these days we are having some issues at server side attimes, I thought we can avoid mismatch of java version between IS and Broker may causing the issue(not sure!). So thought of upgrading the Broker Java version also to java 1.5. Will it help in anyways?
Ideally there should not be any issues. But try to implement in lower environments ( Dev,IT or QA ) and if everything is green then proceed on Prod as we usually have issues with JVM.
In the install directory where Broker is installed there will be a jvm directory at the same level. Under the jvm directory will be another directory with the version as part of its name: for example, jvm150 or jvm160. Can’t confirm that is the same with Java 1.4, so it will still be interesting to hear what SriLakshmi says. But to verify you can run /jvm/jvm160/bin/java -version.